A. Field of Invention
The present application pertains to a beach umbrella, and more particularly, a beach umbrella having a shaft arranged and constructed to provide increased resistance when the umbrella is subjected to wind thereby greatly reducing the likelihood of the shaft being pulled out from the sand.
B. Background of the Invention
Going to the beach is a favorite activity for people of all ages. However, the sun tends to be fairly strong at the beach. Moreover, even during an overcast or hazy day, ultra violet radiation is known to be dangerous and people should not be exposed to it for too long. Exposure to the Sun's radiation is particularly dangerous to young children, and people taking certain medicines. Therefore, to avoid exposure to the Sun's rays people often use a temporary shelter, such as a beach umbrella or a tent, to protect themselves from this harmful radiation. Typically, beach umbrellas include a sheet of fabric or other light-weight material stretched over a generally parabolic shaped frame and secured to the ground by a shaft having a pointed tip so that it can be pushed into the sand, and then removed easily.
One problem with such beach umbrellas is that because they are light and have a large surface area, a gust of wind or even a relatively light breeze can, due to the airfoil-like shape of the canopy generate a lifting force on the surface that tends to pull the shafts out of the ground. When that happens, the beach umbrella is no longer secure, and may be lifted out of the sand and blow away. This is highly undesirable and dangerous because as the shelter is upended and blown away, it can cause serious injury to other beachgoers and damage to property.
A typical beach umbrella includes a generally round canopy having the shape of an inverted bowl and mounted on a frame formed of a plurality of radial wires secured to a vertical center shaft. Many umbrellas are collapsible so that they can be deployed or removed quickly and can be carried easily. Some umbrellas have more complex canopies to accommodate two or more users.
There have been several attempts made in the past to insure that umbrellas are not pulled out of the ground easily by wind, however, none of these attempts were very successful. For example, the canopy of some umbrellas were provided with one or more openings or flaps (usually near the umbrella peaks) that allow air pressure to equalize on its two sides, and thereby reduce the lifting forces from wind. However, these vents render the structure of the umbrella significantly, hence umbrellas with vents are more expensive and the vents alone are not always sufficient to prevent the umbrella from being lifted by a wind gust.
Another proposed solution involved reducing the radius of curvature of the canopy (e.g., by making it flatter). However, it is difficult to make and operate such umbrellas because the forces on ribs become very large, and such umbrellas do not provide as much shade if the Sun's rays are at a low angle.
Umbrellas and other temporarily shelters are also sometimes anchored by guy wires extending at an angle from the canopy to several anchoring points. These arrangements require a much larger space than the area actually covered by the temporary shelter itself. Moreover the guy wires are expensive, unsightly, and represent a tripping hazard.
Umbrellas with a helix secured to the bottom of the shaft have been suggested. However this arrangement requires a very large insertion torque that can be developed only by adding handles or other perpendicular arms to the shaft. This handles are arm are expensive, render the shaft more complex, and esthetically they are unsightly.
Another suggested solution included a rotatable helix added to the shaft tip. Internal gearing was provided inside the shaft for selective rotation of the helix. This solution also renders the shaft more complex and expensive to manufacture. Moreover, the proposed structure is prone to failure over time due to rust forming on the internal gearing due to the intense humidity and salinity of the air from the ocean nearby, and the probability that no matter what precautions are taken, sand will eventually clog the internal gearing.
Yet another suggested solution included adding helical wings on the shaft using screws or other means. Again, this solution increases the complexity and is expensive. Moreover, these wings increase the size of the shelter and its installation on the beach (if they come separately) is difficult, requiring various tools.
In summary, as any beach goer knows only too well, none of the solutions suggested so far have been proven entirely satisfactory, and as a result, even on a relatively calm day, it is not uncommon to see upended umbrellas rolling or flying along a beach and being chased by their unhappy owners.